Maeda was born in Kobe, Japan but spent his childhood in the United States. He was educated at and played for Gyosei Junior High and Ghosei High School in Tokyo. While he was a high school student, he was chosen as one of the Designated Players for Development by J. League and JFA. Because of this status, Maeda was able to register as a Verdy Kawasaki player while he was still eligible to play for his high school club. However, he did not play any official match for Verdy.
After graduating from his high school in 2000, he joined Jubilo Iwata. His first appearance as a professional player came on 3 May 2000 in a league match against Kawasaki Frontale. His first professional goal came on 28 August 2001 in a J. League Cup game against JEF United Ichihara. In the season 2009 was the J. League Top Scorer with twenty goals. In the 2010 season, Maeda became the top scorer again, netting 17 times.
Since the 2007 season, for 6 straight seasons, each team Maeda scores his first goal of the league campaign against has eventually been relegated to J. League Division 2. This has given rise to the so-called "curse of (Ryoichi) Maeda". It became a topic of wide public conversation in late 2012 as Gamba Osaka, the team that he scored his first goal of that season against, was in the relegation zone despite having not ranked lower than 3rd in the previous 3 seasons. Consistent with the "curse", Gamba Osaka was relegated to J2 following the last game of the season in which they lost against, funnily enough, Jubilo Iwata 2–1 with Maeda scoring a goal and an assist. The curse will have come to an end by the end of the 2013 season, however, as Maeda's first goal of the 2013 season came in a loss to Urawa, who will not be relegated.